Electronic structures of disordered Ag-Mg alloys

Abstract

We have calculated the electronic structures of the valence bands in a series of \ensuremath{\alpha}-phase (disordered fcc) Ag-Mg alloys over the range 0--30 at. % Mg using the Korringa-Kohn-Rostoker method within the coherent potential approximation (KKR-CPA). We find that the variation of the equilibrium lattice constant with composition is in good agreement with experimental measurements. The bandwidth of the Ag-related d states decreases with the addition of Mg although the position of the bottom of the band remains roughly fixed in energy with respect to the Fermi level; an observation that is consistent with photoemission measurements. The electronic spectral densities are very sharply peaked at the Fermi energy with widths that are 1% of the Brillouin zone dimension and so the Fermi surfaces of the alloys are well defined throughout the zone. The radius of the neck at the L point and the belly radii in the \ensuremath{\Gamma}X and \ensuremath{\Gamma}K direction increases approximately linearly with increasing Mg content. Taking into account some previous work on the origin of the short range order in Ag-rich alloys, we conclude that the local-density approximation KKR-CPA method provides a realistic description of the electronic structure in \ensuremath{\alpha}-phase Ag-Mg alloys.